a missing slot asks, whatever the confidence (V-557)

The clarify path was gated on dec.Clarify, so a turn the cascade routed
confidently but incompletely skipped it. "напомни позвонить" reached applyAction,
failed on the missing time and parked nothing, and the "в семь вечера" that
followed was routed as a world question and web-searched.

The gate now also fires when missingFor names a required slot. A bare capture
verb gets a stage-0 rule of its own: it was reaching the resident model as chat,
which answered by agreeing to a wording change nobody asked for.

cmd/mavend/voicewire.go

@@ -404,6 +404,10 @@ func buildRouter(emb router.Embedder, acts router.ActMatcher, threshold float64,
 	// board noun), and before the capture marker, which would otherwise read
 	// "убери из задач купить молоко" as a new task (Vikunja #512).
 	grammars = append(grammars, router.TaskStatusGrammar())
+	// Before the capture markers, which all need an object. A capture verb
+	// alone is a fact with no key, and the clarify path asks for it rather than
+	// letting the model invent an answer (Vikunja #557).
+	grammars = append(grammars, router.BareCaptureGrammar()...)
 	grammars = append(grammars, router.TaskCaptureGrammar())
 	// After the capture marker, so "запиши" still wins over "расскажи", and
 	// last overall because it matches on the first word alone: "расскажи про